The present invention relates to a method of and a device for production of hydrocarbons, in particular oil from wells.
Methods and devices of the above mentioned general type are known in the art. One of such methods is disclosed for example in U.S. Pat. No. 5,105,889. The device disclosed in this reference includes a set of axially vertically aligned pipes of different diameters and length, representing a multiparameteric hydrodynamic system which establishes a certain precalculated bottomhole pressure below the device, in order to decrease gas blockage of the near bottomhole zone of the formation and to provide a stable fluid flow to the surface. A forced fluid degassing takes place the device, creating a two-phase gas-liquid emulsion in order to provide a sufficient fluid lift within the well. The device disclosed in this patent has however certain limitations. A pressure differential depends on the calculated diametrical parameters of the pipes, which correspond to current values of parameters of the flow and the formation. Such stringent dependency restricts the adaptability of the device to changing reservoir and well conditions. Geometrical sizes of the pipes on which the efficiency of the device depends are based on such data as reservoir and bottomhole pressure, reservoir collecting properties, physical oil and gas characteristics, etc. The data may not accurately correspond to the actual current conditions resulting in an impaired efficiency of the bottomhole device. In the calculations some operational procedures can not be taken into consideration such as completion and shut-in of an adjacent well, thus impairing well parameters and affecting performance of the well with the bottomhole device. There is however a long period of time from the date when the well and the parameters are taken, than the sizing calculations of the device are performed, and the device is manufactured and installed in the well. During this time the parameters may change and the calculations will be inaccurate.
Another method and device is disclosed in U.S. Pat. No. 5,752,570. In accordance with this patent, bottomhole pressure is automatically maintained higher than a current saturation pressure of the formation fluid with gas in the near bottomhole zone of the formation, regardless of fluctuations of fluid pressure in the formation, in order to create fluid flow with minimum gas content. Once the bottomhole pressure decreases, the device automatically creates conditions for formation of a fluid flow into the device with an increased speed. Nearly monophase flow is transformed within the device into a finely dispersed gas-liquid flow, in order to provide its lift to the wellhead. The device disclosed in this reference automatically adjusts bottomhole pressure to a desired level, simultaneously providing a pressure drop, in order for the fluid to degass within the transforming area, according to the device inlet pressure at the bottomhole. However, in the process of oil field development, operational conditions change as well as the inflow performance curve corresponding to a current well operation, and the sensing element of the device disclosed in this reference will no longer maintain the same optimal well operation, since its calibration was based on the previous well information parameters. Also, in the device disclosed in this reference, the regulation is performed by means of changing an inlet diameter of the device, which is based on extremely little movement of its elements. Besides in case of unstable well operation, the regulating system may acquire automatic fluctuations. Calculations have proven that in some wells a space between the inner nozzle surface and the outer surface of the regulating cone of the device reduces approximately 0.01 inch. With such a small space even a trace of sand in the fluid can jam the regulating unit and stop the well. Since the pressure difference depending on the movement of the regulating cone has a non linear characteristic and is a function of fixed power of the diameter of the regulatable cross-section, it impedes precise regulations.